The OIF's coherent optics work gets a ZR+ rating

The OIF has started work on a 1600ZR+ standard to enable the sending of 1.6 terabits of data across hundreds of kilometres of optical fibre. 

The initiative follows the OIF's announcement last September that it had kicked off 1600ZR. ZR refers to an extended reach standard, sending 1.6 terabits over an 80-120km point-to-point link. 

1600ZR follows the OIF's previous work standardising the 400-gigabit 400ZR and the 800-gigabit 800ZR coherent pluggable optics.      

The decision to address a 'ZR+' standard is a first for the OIF. Until now, only the OpenZR+ Multi-Source Agreement (MSA) and the OpenROADM MSA developed interoperable ZR+ optics.

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Optical transmission: sending more data over a greater reach

• Keysight Technologies' chart plots the record-setting optical transmission systems of recent years.

Source: Keysight Technologies

The chart, compiled by Dr Fabio Pittalá, product planner, broadband and photonic center of excellence at Keysight, is an update of one previously published by Gazettabyte. 

The latest chart adds data from last year's conferences at OFC 2023 and ECOC 2023. And new optical transmission achievements can be expected at the upcoming OFC 2024 show, to be held in San Diego, CA in March.

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Marvell kickstarts the 800G coherent pluggable era

Marvell has become the first company to provide an 800-gigabit coherent digital signal processor (DSP) for use in pluggable optical modules.

The 5nm CMOS Orion chip supports a symbol rate of over 130 gigabaud (GBd), more than double that of the coherent DSPs for the OIF's 400ZR standard and 400ZR+.

Meanwhile, a CFP2-DCO pluggable module using the Orion can transmit a 400-gigabit data payload over 2,000km using the quadrature phase-shift keying (QPSK) modulation scheme.

The Orion DSP announcement is timely, given how this year will be the first when coherent pluggables exceed embedded coherent module port shipments.

This is the year coherent pluggable modules exceed embedded coherent port shipments. Source: LightCounting

"We strongly believe that pluggable coherent modules will cover most network use cases, including carrier and cloud data centre interconnect," says Samuel Liu, senior director of coherent DSP marketing at Marvell.

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Ciena advances coherent technology on multiple fronts

• Ciena has unveiled the industry’s first coherent digital signal processor (DSP) to support 1.6-terabit wavelengths
• Ciena announced two WaveLogic 6 coherent DSPs: Extreme and Nano
• WaveLogic 6 Extreme operates at a symbol rate of up to 200 gigabaud (GBd) while the Nano, aimed at coherent pluggables, has a baud rate from 118-140GBd

Part 1: WaveLogic 6 coherent DSPs

Helen Xenos

Ciena has leapfrogged the competition by announcing the industry’s first coherent DSP operating at up to 200GBd.

The WaveLogic 6 chips are the first announced coherent DSPs implemented using a 3nm CMOS process.

Ciena’s competitors are - or will soon be - shipping 5nm CMOS coherent DSPs. In contrast, Ciena has chosen to skip 5nm and will ship WaveLogic 6 Extreme coherent modems in the first half of 2024.

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The various paths to co-packaged optics

Near package optics has emerged as companies have encountered the complexities of co-packaged optics. It should not be viewed as an alternative to co-packaged optics but rather a pragmatic approach for its implementation.

Co-packaged optics will be one of several hot topics at the upcoming OFC show in March.

Placing optics next to silicon is seen as the only way to meet the future input-output (I/O) requirements of ICs such as Ethernet switches and high-end processors.

Brad Booth

For now, pluggable optics do the job of routing traffic between Ethernet switch chips in the data centre. The pluggable modules sit on the switch platform’s front panel at the edge of the printed circuit board (PCB) hosting the switch chip.

But with switch silicon capacity doubling every two years, engineers are being challenged to get data into and out of the chip while ensuring power consumption does not rise.

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Preparing for a post-pluggable optical module world

Part 1: OIF: ELSFP, XSR+, and CEI-112G-Linear

The OIF is working on several electrical and optical specifications as the industry looks beyond pluggable optical transceivers.

One initiative is to specify the external laser source used for co-packaged optics, dubbed the External Laser Small Form Factor Pluggable (ELSFP) project. 

Nathan Tracy

Industry interest in co-packaged optics, combining an ASIC and optical chiplets in one package, is growing as it becomes increasingly challenging and costly to route high-speed electrical signals between a high-capacity Ethernet switch chip and the pluggable optics on the platform’s faceplate.

The OIF is also developing 112-gigabit electrical interfaces to address not just co-packaged optics but also near package optics and the interface needs of servers and graphics processor units (GPUs).

Near package optics also surrounds the ASIC with optical chiplets. But unlike co-packaged optics, the ASIC and chiplets are placed on a high-performance substrate located on the host board.

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Broadcom discusses its co-packaged optics plans

If electrical interfaces are becoming an impediment, is co-packaged optics the answer? Broadcom certainly thinks so.

One reason for the growing interest in co-packaged optics is the input-output (I/O) demands of switch chips. If the packet processing capacity of such chips is doubling every two years, their I/O must double too.

Alexis BjörlinRepeatedly doubling the data throughput of a switch chip is a challenge.

Each new generation of switch chip must either double the number of serialiser-deserialiser (serdes) circuits or double their speed.

A higher serdes count - the latest 25.6-terabit switch ICs have 256, 100 gigabit-per-second serdes - requires more silicon area while both approaches - a higher count and higher speed - increase the chip's power consumption.

Faster electrical interfaces also complicate the system design since moving the data between the chip and the optical modules on the switch's front panel becomes more challenging.

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